Acoustic wave devices using piezoelectric thin film resonators have been used as filters and multiplexers of wireless devices such as, for example, mobile phones. The piezoelectric thin film resonator has a structure designed to have a piezoelectric film sandwiched between a pair of electrodes. Film Bulk Acoustic Resonators (FBARs) and Solidly Mounted Resonator (SMRs) have been known as the piezoelectric thin film resonator.
When a large electric power is input to the piezoelectric thin film resonator, non-linearity depending on the c-axis direction of the piezoelectric film causes a second harmonic to be generated in an output signal. Thus, there has been known a technique that divides the piezoelectric thin film resonator so that the second harmonic is reduced as disclosed in, for example, Japanese Patent Application Publication Nos. 2008-085989 and 2007-006495 hereinafter referred to as Patent Documents 1 and 2, respectively.
When a resonator is divided so that the second harmonic is reduced as described in, for example, Patent Documents 1 and 2, the number of resonators increases, and the chip size thus increases. In addition, the reduction of the second harmonic may become insufficient because of the parasitic capacitance component of the wiring line connecting divided resonators.